Heretofore, with regard to an alkyl 3-(4-tetrahydropyranyl)-3-oxopropanoate compound, there was a description of a name of methyl 4-tetrahydropyranoyl acetate, but there was no description on information about the synthetic method, physical properties, etc., so that it is doubtful whether the presence thereof could be confirmed or not at that time (for example, see Non-Patent literature 1).
Also, as a process for preparing 4-acyltetrahydropyran which is a starting compound of the present invention, there has been disclosed a method in which, for example, 2,2′-dichloroethyl ether and cyanoethyl acetate are reacted to synthesize ethyl 4-cyanotetrahydropyran-4-carboxylate, the resulting compound is hydrolyzed to prepare 4-cyanotetrahydropyran-4-carboxylic acid, then, the acid is heated under high temperature to synthesize 4-cyanotetrahydropyran, and further, a Grignard reagent is reacted thereto to prepare 4-acetyltetrahydropyran (for example, see Non-Patent literature 2). However, according to this method, multi-step reactions are required, and a Grignard reagent must be used so that the reaction operation or post-treatment becomes complicated, whereby it is not advantageous for an industrial process.    [Non-Patent literature 1] Tezisy Doki.-Sov.-Indiiskii Simp. Khim. Prir. Soedin. 5th, 1978, 16.    [Non-Patent literature 2] J. Am. Chem. Soc., 64, 1672 (1942)